1. Technical Field
The present application relates to a combination tool and a method for metal-cutting machining of a drill-hole and its hole surface, such as, in at least one possible embodiment, for metal-cutting machining of a valve stem bushing and its valve seat, the combination tool comprising a base body including a clamping chuck extending in axial direction for a turning tool for machining holes as well as at least one insert seat radially spaced from a centric longitudinal axis, for receiving a plate-shaped cutting insert. The cutting insert is provided for machining the hole surface and comprises two base sides which are situated opposite each other and connected with each other through small sides. The insert seat includes a base bearing face against which one of the base sides of the cutting insert is clamped in mounted condition. The present application also relates to a plate-like cutting insert for such a combination tool.
2. Background Information
The combination tool serves in particular for intermediate machining and finishing of the valve seat as well as of the valve stem bushing in particular of a motor-vehicle cylinder head.
To essentially assure a defined behavior of the inflow into, and the outflow out of, the combustion space of a motor-vehicle engine, lastingly during the entire lifetime of the engine, the faces of the cylinder head cooperating with an inflow or outflow valve have to be machined with high precision and with only minimum tolerances. In the manufacture of cylinder heads, usually guide bushes and valve-seat rings are fitted into corresponding recesses of an aluminum or cast-iron cylinder head. These guide bushes and valve-seat rings are usually subjected to a two-step machining process in which they are first of all machined intermediately and afterwards finished. For each of these steps, a combination tool is used with which both the cylindrical surface of the guide bush forming the valve stem bushing and the usually conical surface of the valve-seat ring are machined. For machining the valve stem bushing, usually a reamer is used as turning tool. For machining the valve seat, usually several cutting inserts are used, which are distributed over the circumference of the combination tool and are arranged to the axial axis in part at different cone angles, so that the valve seat, viewed in section, has several cone angles and that a kind of curved surface is formed.
To achieve the desired high-precision machining, an essentially exact and very precise concentric running of the combination tool is necessary or often necessary. The centric axes of the individual tool components, i.e. of the turning tool (reamer) as well as of the cutting inserts, must generally or exactly coincide with the axis or rotation. In addition, a very high angular accuracy is desired when setting the cone angle for the valve seat. As for machining a cylinder head, such as, in at least one possible embodiment, in large-batch manufacture, several combination tools are used in parallel and are advanced simultaneously, a very precise and accurate axial orientation of the combination tools to each other is usually also desired.
It should be noted that the preceding background information is for informational purposes only and does not necessarily admit that the subsequently mentioned publications are prior art.